Regulation of calcium signaling by the PKD2 gene product

常染色体显性多囊肾病（ADPKD）是最常见的遗传性疾病之一。千分之一的美国人患有肾、肝和胰腺上皮囊肿。自然发生的两个独立基因PKD1和PKD2的突变是绝大多数（~99%）ADPKD病例的原因。PKD1编码具有长胞外结构域的大质膜蛋白，而PKD2编码TRP超家族的离子通道（目前命名为TRPP2）。我们和其他人已经证明PKD1与TRPP2物理相互作用形成离子通道复合物（PKD1/TRPP2），将细胞外刺激与Ca2+内流联系起来。然而，这些基因的突变如何导致ADPKD仍不清楚。与β -连环蛋白无关的Wnt通路肢体缺陷（非典型Wnt通路）也与膀胱发生有关。我们认为PKD1/ trpp2介导的信号通路与非典型Wnt通路之间存在功能相互作用。我们将通过以下问题来验证这一假设：1)PKD1或PKD2的致病性突变是否会破坏非规范的Wnt信号通路？2) PKD1/TRPP2复合物的激活过程是如何被非规范Wnt通路调节的？3)这两种途径在体内是否相交？这些问题将通过细胞培养、斑马鱼胚胎和小鼠的互补方法来解决。提出的研究将帮助我们了解PKD1和TRPP2的基本特性及其在膀胱发生中的作用。由于ADPKD的病理生理基础尚不清楚，这些实验将为制定治疗策略奠定基础。

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic diseases. It affects 1 in 1000 Americans with the development of epithelial cysts in the kidney, liver, and pancreas. Naturally occurring mutations in two separate genes, PKD1 and PKD2, are responsible for the vast majority (~99%) of all cases of ADPKD. PKD1 encodes a large plasma membrane protein with a long extracellular domain, while PKD2 encodes an ion channel of the TRP superfamily (currently named, TRPP2). We and others have shown that PKD1 physically interacts with TRPP2 to form an ion channel complex (PKD1/TRPP2) that links extracellular stimuli to Ca2+ influx. However, it still remains unknown how mutations in these genes cause ADPKD. Defects in the limb of the Wnt pathway not associated with beta-catenin (non-canonical Wnt pathway) have been also associated with cystogenesis. We propose that there is a functional interaction between PKD1/TRPP2-mediated signaling and the non-canonical Wnt pathway. We will test this hypothesis by asking: 1) Can pathogenic mutations in PKD1 or PKD2 disrupt non-canonical Wnt signaling pathway? 2) How the activation process of the PKD1/TRPP2 complex is modulated by the non-canonical Wnt pathways? And 3) Do these two pathways intersect in vivo? These questions will be addressed by complementary approaches in cell culture, zebrafish embryos, and the mouse. The proposed studies will help us understand fundamental properties of PKD1 and TRPP2 and their roles in cystogenesis. As the pathophysiological basis of ADPKD is unknown, these experiments will set the stage for the development of therapeutic strategies.